As is known, there is an increasing need for protection against the penetration of contaminants into a sheltered space, given by the threat of military attacks and by acts of terror using NBC means of warfare. Such protection is provided by the use of shelters and protected spaces located inside buildings. Shelters are provided with professional NBC air filtering systems including blowers, which create an overpressure inside the protected space and provide cleaned and filtered air. The overpressure is important in order to ensure a clear direction of airflow from inside the protected space to the outside atmosphere, through ever-present vents in the walls of the shelter, the door or the window seals. Use of this method assures that no contaminated air will penetrate into the protected space.
Due to the potential of terror attacks, shelters can no longer provide the degree of required protection, but complete facilities or parts of buildings have to be pressurized using airtight windows and other required elements.
Furthermore, due to the terrible advancement in warfare and warfare agents, the need for use of a comprehensive protection system, especially the NBC-system, in a 24 hour/7 day mode, has risen, since in the event of a “silent terror attack”, no alert is given and the threat is neither obvious to the population, nor to the experts. Therefore, entire buildings have to be protected and used at all times under conditions such as those under a terror attack. For such a use, the costs of the NBC-filter material and the energy to constantly operate the systems are very large. The need for a system and method that allow the achievement of reliable protection in the 24/7 mode with acceptable costs, is required.